Portable humidifying devices, or humidifiers, are used to moisturize the ambient air in a room, most commonly, a single room of a home. Different types of humidifiers are available in both the warm and cool mist varieties. Evaporative humidifiers, or wick humidifiers, utilize a reservoir of water, from which the wick draws moisture, and a fan which forces air through and/or past the wick, thereby picking up moisture as the air is directed through a spout or vent into the room. Ultrasonic humidifiers utilize nebulizers or ultrasonic transducers, a metal diaphragm vibrating at ultrasonic frequency, to cause a fog or mist fanned of small water droplets to rise from the surface of a reservoir containing the transducer and out of a directed opening into the room. Similarly, impeller humidifiers break water into small droplets through a rotating disc that directs the water through a diffuser. Because evaporative, ultrasonic and impeller humidifiers do not heat the water, they are commonly referred to as cool mist humidifiers.
Vaporizers or steam humidifiers boil water and release the steam through a spout or vent into the room. However, due to the high temperatures of the steam (>100° C.), it is usually cooled somewhat before being released into the room. Typically, this is done by mixing it with cooling air from a fan to create a warm mist that is safe to users. The cooling air is usually mixed with the steam in a pathway leading to the directed opening into the room to ensure that it is sufficiently mixed and contains no “hot spots.” The smaller the opening into the room, the more it is mixed and the safer the resultant warm mist. Such so-called “warm mist” humidifiers do not produce a true mist because the steam is mixed with cooling air that is not humidified, reducing both output and efficiency. To increase output, the steam is superheated, thus further increasing the risk of getting burned.
However, humidifiers having a combination of warm and cool mist do not typically boil the water. Rather, these combination humidifiers merely heat the water, usually in a connecting tube extending to the nebulizer.
Warm mist humidifiers, though typically consuming more power, also purify the mist through boiling to kill bacteria in the water, while cool mist humidifiers must be cleaned regularly to prevent the accumulation of bacteria and contamination of the air caused by the projection of said bacteria with the mist. Regardless of type, most humidifiers utilize a removable and fillable water tank and a housing with a directed opening, or output vent, which serves to mix and concentrate the mist into the room such that it is projected with sufficient velocity for the droplets to spread apart and humidify a larger volume of the air in the room, not just the air near the humidifier.